S01 - Session O6 - The role of salicylic acid responsive genes in disease resistance in Brassica rapa vegetables

Authors: Naomi Miyaji, Mst Arjina Akter, Motoki Shimizu, Takeshi Takasaki-Yasuda, Elizabeth Dennis, Ryo Fujimoto *

Salicylic acid (SA) is a plant hormone that regulates many stress responses and developmental processes, including the plant immune response, thermogenesis, senescence and abiotic stress responses. To identify SA-responsive genes at the whole genome level, we performed RNA-sequencing analysis with and without SA treatment in two komatsuna ( Brassica rapa var. perviridis ) cultivars. We identified 1061 up- and 994 down-regulated genes that overlapped between the two lines, and these genes were defined as B. rapa SA-induced genes (BrSAIGs) and B. rapa SA-suppressed genes (BrSASGs), respectively. Only 5.6% of BrSAIGs overlapped with SA-induced genes in Arabidopsis thaliana , indicating that most SAIGs differ between species. We examined how many B. rapa genes categorized into the GO term 'response to SA stimulus' showed a change of expression with SA treatment and approximately 20% of these genes were identified as BrSAIGs or BrSASGs. This low percentage might be due to the GO classification being based on an A. thaliana database, while the actual SA-responsive genes in B. rapa might be different. We examined the relationship between genes whose expression was altered by the pathogen infection and SA-responsive genes. In case of the hemibiotrophic pathogen Fusarium oxysporum f. sp. conglutinans ( Foc ), we identified genes induced by SA and specifically upregulated by Foc inoculation in a Fusarium yellows resistant line, suggesting that these genes play a role in the defense response to Foc . The SA responsive genes identified in this study will be useful for defining the importance of SA in stress responses and developmental processes, including Fusarium yellows resistance in B. rapa .